org

Ala

n

Available online 30 June 2011

nat

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the cost-effectiveness is also expected to improve by making betteruse of a common infrastructure and the economy of scale of thesteam turbine [3]. Finally, considerable additional savings ofgreenhouse gas emissions come from the production of fresh water,since the majority of desalination plants are currently fed by powerproduced by fossil fuels.

be separated from the coast. To solve all of these issues, specicscientic research, techno-economic analysis and demonstrationplants are needed to dene the best concepts and schemes of theintegration of a desalination plant into a CSP plant.

More specically, a techno-economic analysis has been per-formed for the combination of parabolic-trough (PT) power plantsfor electricity production with MED and ultraltration/RO plants intwo sites in Israel (Ashdod) and Jordan (Aqaba) [11]. An analysiswas carried out taking into account the same fresh water

* Corresponding author. Tel.: 34 950387941; fax: 34 950365015.

Contents lists availab

er

els

Energy 36 (2011) 4950e4958E-mail address: guillermo.zaragoza@psa.es (G. Zaragoza).make possible large concentrating solar power (CSP) plantsdevelopments in arid regions, such as the Desertec initiative [1].These regions suffer from a serious lack of fresh water availability,which could jeopardize the deployment of the CSP plants. Theintegration of desalination technology into CSP plants to producewater and electricity at the same time, could solve the water andenergy problems in many of the worlds arid areas [2]. CombiningCSP and Desalination facilities (concentrating solar power anddesalination (CSPD)) benets the identication of technologicalsynergies that could reduce the cost of combined power anddesalination production against independent plants. In addition,

of CSP plants coupled with desalination systems (reverse osmosis(RO) and multi-effect distillation (MED)) has been shown for theMiddle East and North Africa (MENA) region [9,10]. Besides all thepotential benets of combining power and water productionshown, the integration of desalination processes and technologiesinto CSP plants is not yet a straightforward issue and many tech-nological aspects remain to be discussed. The CSPD conceptneeds, obviously, facilities to be located near the sea, where landcost and availability could be a signicant problem. Moreover, thesolar direct normal irradiance (DNI) is normally lower on areasclose to the sea, which makes CSP plants most optimal locations toKeywords:Solar energyConcentrating solar power (CSP)System integrationThermodynamic simulationSteam cyclesDesalination

1. Introduction

Many projects are currently under0360-5442/$ e see front matter 2011 Elsevier Ltd.doi:10.1016/j.energy.2011.05.039for coupling parabolic-trough (PT) solar power plants and desalination facilities in a dry location rep-resenting the Middle East and North Africa (MENA) region. The integration of a low-temperature multi-effect distillation (LT-MED) plant fed by the steam at the outlet of the turbine replacing the condenser ofthe power cycle has been simulated and compared with the combination of CSP with a reverse osmosis(RO) plant. Furthermore, an additional novel concept of concentrating solar power and desalination(CSPD) has been evaluated: a LT-MED powered by the steam obtained from a thermal vapourcompressor (TVC) using the exhaust steam of the CSP plant as entrained vapour and steam extractedfrom the turbine as the motive vapour of the ejector. This new concept (LT-MED-TVC) has been analyzedand compared with the others, evaluating its optimization for the integration into a CSP plant byconsidering different extractions of the turbine.

2011 Elsevier Ltd. All rights reserved.

sion and preparation to

Several studies on different basic integrated power and desali-nation plants (IPDP) congurations have been published [4e8].However, not so many deal with solar power plants. The potential9 May 2011Accepted 20 May 2011a thermal desalination unit. This paper presents a thermodynamic evaluation of different congurationsReceived in revised formconsidered for the planned installation of CSP plants in arid regions. There are interesting synergiesbetween the two technologies, like the possibility of substituting the condenser of the power cycle forAssessment of different congurations fpower and desalination plants in arid re

Patricia Palenzuela, Guillermo Zaragoza*, Diego C.Julin BlancoCIEMAT-Plataforma Solar de Almera, Ctra. de Sens s/n, 04200 Tabernas, Almera, Spai

a r t i c l e i n f o

Article history:Received 1 March 2011

a b s t r a c t

The combination of desali

En

journal homepage: www.All rights reserved.combined parabolic-trough (PT) solarions

rcn-Padilla, Elena Guilln, Mercedes Ibarra,

ion technology into concentrating solar power (CSP) plants needs to be

le at ScienceDirect

gy

evier .com/locate/energy

production and electrical power generation capacity. The resultsshowed that the CSPRO setup has economic benets in compar-ison to the CSPMED conguration using a wet cooling system forthe power block. Another technical and economic study for waterdesalination and CSP power plants in different MENA countries hasbeen presented but this time considering a dry cooling system forthe turbine [12]. For each location, four congurations wereanalyzed, combining two types of solar technologies (PT and linearFresnel reector) and two types of desalination processes (low-temperature multi-effect distillation (LT-MED) and RO). The mainresult was that in most cases studied the solar eld required for theCSPRO was larger than for the CSPLT-MED, due to the higherelectrical consumption of the RO overcompensating the lowerthermal efciency of the turbine of the MED case.

This paper presents a thermodynamic evaluation of differentcongurations for coupling PT solar power plants and desalinationfacilities in aMENA location (Abu Dhabi). The typical congurationsof combining CSP with a RO desalination plant and a LT-MED plantfed by the steam at the outlet of the turbine have been studied.However, an additional concept of CSPD has been evaluated forthe rst time in this kind of analysis: a LT-MED powered by thesteam obtained from a thermal vapour compressor (TVC). In thiscase, unlike in the typical thermal vapour compression MEDprocess (TVC-MED), the entrained vapour to be used in the steam

working uid. The solar plant consists of PT (LS-3 type) collectorsaligned on a northesouth orientation and a thermal storage tank toprovide additional operation when solar radiation is not available.The collectors track the sun from east to west during the day toensure it is continuously focused on the linear receiver. Differentdesalination systems have been considered for combination withthis CSP plant. A dry cooling system is considered for condensingthe exhaust steam form the turbine in the power block, which is theusual means in arid areas, since the typical wet cooling towersconsume between 2 and 3 metric tons per MWh [13].

The PT-CSP technology is the same in all the congurationsassessed. Steam at point A is generated from the thermal energycollected by the solar eld. It is subsequently sent to a HP turbinewhere, after suffering an expansion process is extracted at B inorder to reheat it. The reheated steam is left to its expansionthrough a LP turbine to obtain the required power. The expansion isup to state point D in all cases except that of Fig. 2, where theexpansion is only up to state point E.

Conguration #1 corresponds to the basic combination of a ROdesalination plant with a PT-CSP plant. In this case (Fig. 1) thedesalination process is driven by the power output from the CSPplant. This conguration has the advantage that the desalinationprocess is completely independent from the power generation andcan be even separated geographically.

P. Palenzuela et al. / Energy 36 (2011) 4950e4958 4951ejector comes from the exhaust steam of the CSP plant instead of anintermediate effect of the desalination plant. Within this concept(LT-MED-TVC), different schemes must be studied: a system thatuses the high exergy steam from the high pressure (HP) turbineoutlet as motive steam in the TVC, and others that use steamextracted at different pressures from the low pressure (LP) turbineas the motive steam in the ejector.

2. Methodology

2.1. Description of the systems

The systems under consideration are described in Figs. 1e4.They each consist of a parabolic-trough concentrating solar power(PT-CSP) plant based on a reheat Rankine cycle with water as theFig 1. Diagram of Conguration #1 (RO uConguration #2 corresponds to a LT-MED integrated into a PT-CSP by replacing the conventional cooling unit of the steam cycle. Inthis case (Fig. 2), the desalination plant is fed by the LT steam fromthe turbine outlet (at state point F) after being reheated to obtainsaturated steam without increasing the temperature. In this casethe exhaust steam is considered at a slightly higher pressure than inthe previous case, as it must feed the LT-MED desalination plant at70 C.

Congurations #3 and #4 consider LT-MED powered bya thermal vapour compressor (LT-MED-TVC) (Figs. 3 and 4). Theintegration of a LT-MED-TVC unit has a huge interest, since it isuseful for the coupling of any thermal desalination process toa power plant and not only for a MED process. In this case, unlikethe conventional thermal vapour compression process (TVC-MED),the entrained vapour to be used in the ejector comes from thenit combined with a PT-CSP plant).

MED

P. Palenzuela et al. / Energy 36 (2011) 4950e49584952exhaust steam from the LP turbine instead of an effect of the MEDunit. As for the motive steam, two scenarios have been considered,using part of the HP turbine outlet steam or extracting from the LPturbine at different pressures. In Conguration #3 (Fig. 3), part ofthe steam at state point B is used as motive steam in the steamejector after passing through a reheater to achieve saturationconditions. In addition, one part of the exhaust steam from the

Fig 2. Diagram of Conguration #2 (LT-turbine at D is used as entrained vapour in the ejector. The resultingcompressed vapour from the ejector is injected into the rst effectof the distillation unit at F, driving the thermal desalination process.Conguration #4 (Fig. 4) follows a similar concept, but in this casea fraction of superheated steam extracted from the LP turbine at Gis used as motive steam in the ejector.

Fig 3. Diagram of Conguration #3 (LT-MED-TVC unit integration intoThe operating conditions considered in the schemes proposedare indicated in Table 1. These values have been used as inputs forthe subsequent simulations. The net power of the CSP plant hasbeen considered in all congurations to be 50 MWe, which is thenormal size of a commercial PT-CSP plant [14]. The size of thedesalination plants has been determined by dimensioning the LT-MED in order to replace the condenser of the power plant in

unit integration into a PT-CSP plant).Conguration #2 (all the exhaust steam coming from the LP turbineis used to drive the desalination plant producing fresh water). Oncethe right size of the LT-MED has been determined considering 24 hoperation, the same size has been assumed for the desalinationplants considered in the other congurations, including the ROunit. As can be observed in Table 1, another common condition for

a PT-CSP plant using motive steam from the HP turbine outlet).

outlet of the turbine and houtlet,i is the ideal enthalpy of the steam

PT-

P. Palenzuela et al. / Energyall the proposed congurations is that the steam is allowed to beexpanded up to 58 C (0.18 bar), except in Conguration #2 wherethe expansion is up to 70 C (0.31 bar). This is the result of the use ofdry air condensers, which is the only feasible option for solar powerplants in these arid regions [4], unlike the wet cooling towers thatare used in other regions to achieve maximum performance.

Fig 4. Diagram of Conguration #4 (LT-MED-TVC unit integration into a2.2. Analysis of the systems

In this section, both the integrated power and desalinationfacility, and the solar eld are analyzed.

2.2.1. Integrated power and desalination facility analysisA steady state model has been made by proposing a set of

nonlinear, algebraic equations for each cycle and implementingthem in the Engineering Equation Solver (EES) software [15]. Thethermodynamic state points used are those of Table 1. For eachcycle, the net output thermal capacity (thermal power to beprovided by the solar eld), overall efciency, and thermal powerdissipated in the condenser have been calculated.

Actual expansion and compression processes in the turbines andpumps, respectively, have been considered in the model. An isen-tropic efciency of 85% has been assumed for all the turbines andpumps. The actual steam enthalpy at the outlet of the HP and LPturbines has been calculated through:

Table 1Operating conditions dened for the schemes shown in Figs. 1e4.

Point in the diagram Parameters Values

A Pressure and temperature 371 C, 104 barB Pressure 17 barC Pressure and temperature 371 C, 17 barD Temperature 58 CE Temperature 70 CF Temperature 70 CG Pressure 2, 4, 6, 10, 16 barhst hinlet houlethinlet houtlet;i

(1)

where hst is the isentropic efciency, hinlet is the enthalpy of thesteam entering the turbine, houtlet is the actual enthalpy at the

CSP plant, with extractions from the LP turbine used as motive steam).

36 (2011) 4950e4958 4953leaving the turbine. In the case that some steam is extracted fromthe turbine (Fig. 4), the enthalpy of the extracted steam has beencalculated with the assumption of linear condition line in the hesdiagram between the inlet and the outlet of the turbine:

hm houtlethinlet houtlet

sm soutletsinlet soutlet

(2)

where hm and sm are the enthalpy and the entropy at the pointwhere the steam extraction is done.

In all case studies, the analysis has been carried out consideringa net power production of the plant (Pnet) of 50 MWe. The netpower production of the plant is calculated as the gross turbineoutput (Pturb) minus the power required by the pumps (Ppumps), thedesalination plant (P) and the cooling unit (Pcooling):

Pnet Pturb Ppumps Pdesal Pcooling (3)For the calculation of the power required by the desalination

plant, a specic electric consumption of 2.5 kWh/m3 has beenconsidered in the case of the MED plant, and 5.6 kWh/m3 for theRO, which are the estimated values for Abu Dhabi [9] (the highvalue is due to the high salinity and temperature of the Persian Gulfseawater). In both cases 24 h operation has been taken intoaccount. The power required by the cooling unit has been takenfrom a study of a dry-cooled PT plant located in the Mojave Desert,which showed 5% less electric energy produced annually [13]. InCongurations #3 and #4, since not all the steam is driven to thecondenser the energy consumption due to the dry cooling is pro-portionally lower.The steam ow required by the MED desalinationplant has been calculated by:

Fig 5. Results obtained in the simulation of Conguration #2 (LT-MED plant integration into a PT-CSP plant).

P. Palenzuela et al. / Energy 36 (2011) 4950e49584954qsteam FWF rGOR (4)

where FWF is the fresh water production in m3/day, r is the fresh3 water density in kg/m (at 35 C and 1 bar) and GOR is gained

Fig 6. Results obtained in the simulation of Conguratoutput ratio, which is dened as the amount of distillate producedfor every mass unit of steam supplied to the distillation unit. A GORof 9.8 has been considered in all cases of MED technology.

To calculate the steam ejector ow rates (bothmotive steam andentrained vapour ow rates), a semi-empirical model developed byion #1 (RO plant combined with a PT-CSP plant).

on #

P. Palenzuela et al. / Energy 36 (2011) 4950e4958 4955El-Dessouky has been used [16]. The model makes use of the elddata collected over 35 years by Power [17] for vapour entrainmentratios of steam jet ejectors. The entrainment ratio is the ow rateratio of the motive steam and the entrained vapour, and can becalculated from the following correlation [16]:

Ra 0:296 Ps1:19

Pev1:04PmPev

0:015PCFTCF

(5)

where Pm, Ps and Pev are the pressures of the motive steam,compressed vapour and entrained vapour respectively, PCF is the

Fig 7. Results obtained in the simulation of Conguratimotive steam pressure correction factor and TCF is the entrainedvapour temperature correction factor. The following two equationshave been used to calculate PCF and TCF [16]:

PCF 3 107Pm20:0009Pm 1:6101 (6)

TCF 2 108Tev20:0006Tev 1:0047 (7)where Pm is expressed in kPa and Tev in C.

Finally, the overall efciency has been calculated by:

hglobal PnetNOTC

(8)

where NOTC is the net output thermal capacity, which is given by:

NOTC Ppcs PRH (9)

Table 2NOTC, overall efciency, cooling requirements, number of collectors per row, number of ro#3 as shown in Figs. 5e7. The different options that can be considered under Congurat

Conguration NOTC(MWth)

Overallefciency (%)

Coolingrequirements (%)

Numper r

#1 205 24.4 100 2#2 188 26.6 0 2#3 231 21.6 36 2where Ppcs and PRH are the power required by the power conversionsystem (consisting of a pre-heater, an evaporator and a super-heater) and by the reheaters of the cycle, respectively.

2.2.2. PT eld analysisConsidering the NOTC of the system, the solar eld size has been

determined by a computer model developed in MATLAB. For thispurpose, a model has been used for the collector based on itsthermal losses, its efciency curve and energy balances [18e20].The model input parameters are listed below:

3 (LT-MED-TVC plant integration into a PT-CSP plant). Northesouth orientation. Design point: 22nd September (radiation at solarnoon 849.728W/m2, ambient temperature 38.4 C).

Thermal storage capacity for 24-h solar operation at design day(fossil backup when the solar radiation is not available).

The net output thermal capacity of the power block. Inlet temperature to the solar eld: 295 C. Outlet temperature from the solar eld: 390 C.

The simulationwas carried out for a location in Abu Dhabi, in theUnited Arab Emirates (longitude: 54.420 east; latitude: 24.470north). With around 1925 kWh/m2 yr DNI radiation [21], this site isa good representative for CSP plants in arid areas. Radiation andambient temperature data have been taken from an availabletypical meteorological year (using Meteonorm DNI proles butnormalizedwith the real measurement of the annual average of theDNI given above). The PT solar eld is based on the commercial LS-3

ws and aperture area resulting from the simulations of the Congurations #1, #2 andion #4 are analyzed in further gures.

ber of collectorsow

Numberof rows

Aperturearea (m2)

LEC(V/kWh)

LWC(V/m3)

989 1,078,010 0.218 0.644908 989,720 0.207 0.703

1117 1,217,530 0.237 0.704

ejector. Subsequently, only 46.63 kg/s enter the LP turbine. Out of

Fig 8. NOTC for different pressures of the steam extracted from the LP turbine inConguration #4 and its comparison to the NOTC needed in Conguration #1.

Fig 10. Overall efciency for different pressures of the steam extracted from the LPturbine in Conguration #4 compared to that of Conguration #1.

P. Palenzuela et al. / Energy 36 (2011) 4950e49584956that, since 29.82 kg/s are used as entrained vapour in the ejector,only 16.81 kg/s are sent eventually to the condenser. On the otherhand, in Conguration #1, all the steam from the LP turbine outlet(63.07 kg/s) must be condensed.type collector, i.e. an aperture area of 545 m2 and a length of 99 m.The peak optical efciency for this type of collectors is 76% and thethermal oil that circulates through the absorber tubes is MonsantoVP-1 (its properties are determined using Monsanto software).

3. Results and discussion

Firstly, the analysis of the power block corresponding toConguration #2 has been carried out in order to determine themaximum water production. The results obtained are shown inFig. 5. A water production of 48,498 m3/day is obtained when allthe steam from the turbine outlet at 70 C (56.94 kg/s) feeds theMED unit. This value has been taken as a xed input parameter forthe rest of congurations analyzed within this work.

Secondly, simulations have been performed for Congurations#1 and #3. The results obtained are depicted in Figs. 6 and 7. In therst case, more steam than in Conguration #2 must be generated,as more total power needs to be generated in the CSP plant in orderto feed the RO desalination plant and the dry cooling unit whilekeeping the same global production of 50 MWe. In the second case(Fig. 7), even more steam must be generated for the HP turbine(73.74 kg/s), since 27.11 kg/s are later used as motive steam in theFig 9. Aperture area for different pressures of the steam extracted from the LP turbinein Conguration #4 compared to that of Conguration #1.Table 2 presents a summary of the NOTC, the overall efciencyand the size of the required solar eld from the full thermodynamicsimulations of Figs. 5e7. It also shows the cooling requirements,which have been assessed as the fraction of the steam ow rate thatleaves the LP turbine and cools in the condenser. Some economicresults are also summarized within this table. An estimation of thelevelized electricity cost (LEC) and levelized water cost (LWC) [22]is given for the three congurations based on the available datafrom real plants [23]. However, since no CSPD plant exists at themoment, the economic corrections due to the coupling are notincluded. This affects especially the case of the thermal desalina-tion. The integration of a LT-MED into a PT-CSP plant by replacingthe cooling unit has a major disadvantage in the fact that thedesalination plant must be very close to the turbine, since theexhaust steam has very low density and therefore pipes with verylarge diameters are needed to conduct the steam to the desalina-tion plant. This is why the thermal compression of the steam (LT-MED-TVC) has also been analyzed.

On one hand, it can be observed that Conguration #2 needs thelowest NOTC and therefore the smallest solar eld. In other words,the decrease in the efciency of the power production for thisconguration due to the higher pressure of the exhaust steam isless than the extra power that the CSP plant must generate inConguration #1 for the RO desalination process and the drycooling system. This result, together with the fact that thisconguration eliminates the cooling requirements of the powercycle, leads to conclude that LT-MED ismore competitive than RO inFig 11. Thermal power dissipated in the condenser for different pressures of the steamextracted from the LP turbine in Conguration #4 compared to Conguration #1.

cost is slightly larger for Conguration #2, considering the total

turbine, the efciency is improved, the more so the lower the

the

aporate

ergyproduction of electricity and water, it does not overcome the factthat the electricity cost is lower.

The results for Conguration #3 show that it needs a largerNOTC than #1 and #2, since it uses high exergy steam to feed thesteam ejector, which results also in a decrease of the overall ef-ciency of the power production. However, if we compare withConguration #1, it can be seen that Conguration #3 requires lesscooling. This fact is reected in the cost, the LEC for the latterconguration is lower than for the former, but in a smallerproportion than the decrease in efciency. These results make theintegration of a LT-MED-TVC plant into a PT-CSP plant an attractiveprospect. However, the concept must be optimized with a moreefcient conguration in terms of the heat extraction. This is thecase of Conguration #4, for which several simulations have beencarried out considering extractions from the LP turbine at differentpressure conditions (point G in the diagram shown in Fig. 4). Theresults obtained have been compared to those of Conguration #1and represented in Figs. 8e11. The detailed simulation results ofeach case are summarized in Table 3.

The NOTC required and the aperture area increase with thepressure of the steam extracted from the LP turbine (Figs. 8 and 9respectively). Also, the lower the pressure of the steam is, thelarger the overall efciencies of the system result (Fig. 10). More-over, energy losses to the ambient due to the cooling process of thepower cycle are much lower at all cases in Conguration #4 than inConguration #1 (Fig. 11), although they increase with the pressureof the steam extracted from the turbine.

As can be observed in Figs. 8e11, in the case of extraction fromthe LP turbine at pressures around 2 bar. Conguration #4 is verysimilar to Conguration #1 in terms of efciency. However, thethermal power dissipated in the condenser is 17 MW, while inConguration #1 is 140 MW.

4. Conclusions

A thermodynamic analysis of several congurations of CSPDtheMENA regions, as opposed to other regions wherewet cooling isused and RO desalination plants have lower specic consumption[11]. The economic estimations support this. Although the water

Table 3Results obtained in the simulation of Conguration #4 using the steam extracted fromcondenser are given, together with the cooling requirements.

Pressure of thesteam extracted (bar)

Motive steam massow rate (kg/s)

Entrained vmass ow

2 32.61 24.324 31.28 25.656 30 26.9410 27.92 29.0216 26.97 29.97

P. Palenzuela et al. / Enplants has been carried out within this work. The systems havebeen modelled for the ambient conditions of arid regions whichimpose dry cooling in the power plant. In all cases, 50 MWe and48,498 m3/day have been considered as net power and waterproduction respectively, and 58 C (0.18 bar abs) the exhaust steamoutlet turbine conditions.

The results show that for the simulated conditions, the inte-gration of a LT-MED unit into a PT-CSP replacing the condenser ofthe exhaust steam of the turbine is more efcient thermodynami-cally than the coupling of the CSP plant with a RO desalination plantand needs a smaller solar eld for the same production of electricityand water. Although by using the steam from the outlet of theturbine to feed the LT-MED plant the power production is reduced,pressure of the extracted steam is. For a value of 2 bar, the resultsobtained in the integration of the LT-MED-TVC desalination unitinto the CSP plant are very similar to those obtained with CSPRO.Actual extractions in commercial plants take place at 2 and 10 bar.Therefore, in the rst case the integration of a MED plant withthermo-compression can also be a valid option for a CSPDconguration in arid regions, especially considering the lowercooling requirements of this case compared to the CSPRO.

Nomenclature

CSPD concentrating solar power and desalinationDNI direct normal irradianceEES Engineering Equation SolverFWF fresh water ow rate (m3/day)GOR gain output ratiohinlet enthalpy of the steam which enters the turbine (kJ/kg)hm enthalpy at the point where the steam extraction is done

(kJ/kg)houtlet actual enthalpy at the outlet of the turbine (kJ/kg)houtlet,i is the ideal enthalpy of the steamwhich leaves the turbine

(kJ/kg)HP high pressurethe reduction is smaller than in other regions where the cold-endtemperature is lower because wet cooling can be performed.

A novel conguration of MED plant with thermo-compression,named LT-MED-TVC, has also been evaluated within this study. Inthis conguration, low pressure vapour feeding the steam ejectorcomes from the exhaust steam of the LP turbine instead of any stageof the MED unit. Several conditions have been considered for themotive steam that drives the ejector, from the outlet steam of theHP turbine to several intermediate extractions in the LP turbine.

When the motive steam comes from the HP turbine, the inte-grated CSPD plant requires a larger solar eld than the combi-nation of CSPRO. However, the energy losses to the ambient arelower for the LT-MED-TVC conguration, since the plant coolingneeds decrease from the CSPRO case.

When the motive steam comes from extractions from the LP

LP turbine at different pressures. Mass ows of the steam entering the ejector and the

ur(kg/s)

Exhaust steam massow rate (kg/s)

Cooling requirements (%)

7.62 2410.93 3012.6 3214.28 3316.34 35

36 (2011) 4950e4958 4957IPDP integrated power and desalination plantsLEC levelized electricity cost (V/kWh)LEW levelized water cost (V/m3)LT-MED low-temperature multi-effect distillationLT-MED-TVC low-temperature multi-effect distillation powered by

a thermal vapour compressorLP low pressureMENA Middle East and North AfricaNOTC net output thermal capacity (MW)PCF motive steam pressure correction factorPdesal power required by the desalination plant (MW)Pnet net power production of the CSPD system (MW)Ppcs power required by the power conversion system (MW)

Pev pressure of the entrained vapour (kPa)Pm pressure of the motive steam (kPa)Ppumps power required by the pumps (MW)PRH power required by the reheaters of the cycle (MW)Ps pressure of the compressed vapour (kPa)PT parabolic-troughPturb gross turbine output (MW)qsteam feeding steam ow rate to the desalination plant (kg/s)Ra entrainment ratioRO reverse osmosissm entropy at the point where the steam extraction is done

(kJ/kg C)TCF entrained vapour temperature correction factorTVC-MED thermal vapour compression multi-effect distillationr fresh water density (kg/m3)hst isentropic efciency of the turbine

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Assessment of different configurations for combined parabolic-trough (PT) solar power and desalination plants in arid regions1 Introduction2 Methodology2.1 Description of the systems2.2 Analysis of the systems2.2.1 Integrated power and desalination facility analysis2.2.2 PT field analysis

3 Results and discussion4 Conclusions Nomenclature References